Solid propellant and propellant burning rate catalyst system



United SOLID PROPELLANT AND PROPELLANT BURN- ING RATE CATALYST SYSTEM No Drawing. Filed Nov. 30, 1956, Ser. N 625,553

26 Claims. (Cl. 60-354) This invention relates to a burning rate catalyst system for solid propellants. In one aspect, this invention relates to an improved propellant having an increased burning rate. In another aspect, this invention relates to an improved method of developing thrust by employing solid propellants of increased burning rate having an improved burning rate catalyst system incorporated therein.

Solid propellants can be classified with respect to composition as double base type, single base type, and composite type. An example of a double base propellant is ballistite which comprises essentially nitroglycerine and nitrocellulose. Examples of single base propellants are nitrocellulose and trinitrotoluene. Composite type propellants are generally composed of an oxidizer, and a binder or fuel. They may contain other materials to improve fabrication or increase ballistic performance such as a burning rate catalyst.

Rocket propellants have achieved considerable commercial important as well as military importance. let propulsion motors of the type in which the propellants of this invention are applicable can be employed to aid a heavily loaded plane in takeoff. Said motors can also be employed as an auxiliary to the conventional power plant when an extra surge of power is required. Said motors can also be employed to propel projectiles and land vehicles. Said propellants can also be used for uses other than propulsion. For example they can be used as gas generators in starting devices, power units where a fluid is employed as a motive force, and other applications where a comparatively large volume of gas is required in a relatively short period of time.

. Solid propellants having relatively slow burning rates are entirely satisfactory for use in JATO units, i.e., rocket units employed as jet assist take oft" units which aid in powering loaded aircraft during take off. However, many of said propellants having relatively slow :burning rates are not entirely satisfactory for use where a propellant having a relatively high burning rate is re- .quired so that maximum thrust can be developed in minimum time as in booster rocket applications, or in said gas generator systems.

I have discovered that a burning rate catalyst system comprising essentially ammonium dichromate, powdered .copper metal or a selected copper compound, and a salt of a trinitrophenolic compoundis effective in increasing the burning rate of solid propellants having relatively slow burning rates to the extent that said propellants can be used where propellants having high burning rates are required. The burning rate of propellants containing the three component burning rate catalyst system of my invention is considerably higher than the burning rate of propellants containing any one or any pair of the components of my catalyst system.

An object of this invention is to provide an improved burning rate catalyst system. Another object of this invention is to provide a burning rate catalyst system comtates atent O 2,969,638 Patented Jan. 31, 1961 prising essentially ammonium dichromate, powdered copper metal or a selected copper compound, and a salt of a trinitrophenolic compound. Another object of this invention is to provide an improved propellant composition comprising a binder component, an oxidizer component, and said burning rate catalyst system. Another object of this invention is to provide an improved gas generation system. Still another object of this invention is to provide an improved method of developing thrust which comprises burning said improved propellant in the combustion chamber of a rocket motor. Other aspects, objects and advantages of the invention will be apparent to those skilled in the art in view of this disclosure.

Thus according to the invention, there is provided a burning rate catalyst system comprising essentially ammonium dichromate, a copper component selected from the group consisting of finely divided copper metal, copper chromite, and copper oxide, and a salt of trinitrophenolic compound selected from the group consisting of 2,4,6-trinitrophenol and 2,4,6-trinitroresorcinol.

Further according to the invention, there is provided an improved solid propellant comprising a binder component, an oxidizer component, and the above described burning rate catalyst system.

Still further according to the invention, there is proof my catalyst system can vary in the range between 3- and 10 parts by weight based on the total catalyst system. Said ammonium .dichromate should be ground as finely as possible, preferably less than 15 microns in size.

The copper component of my catalyst system can be powdered copper metal, copper chromite, or a copper oxide, either cuprous or cupric oxide. Cuprous oxide is presently preferred over cupric oxide. Copper chromite is the presently most preferred copper component. The amount of the copper component of my catalyst system can vary in the range between 0.5 and 7 parts by weight based on the total catalyst system. Said copper component should be ground as fine as possible, preferably to a size of less than 15 microns.

The trinitrophenolic salt component of my catalyst system can be any salt of 2,4,6-trinitrophenol (picric acid), or any salt of 2,4,6-trinitroresorcinol (styphnic acid). The amount of trinitrophenolic salt employed in my catalyst system should be at least 2 parts by weight based on the total catalyst system. It is preferred to use not more than 20 parts by weight of the total catalyst system. The particle size of said trinitrophenolic salt is preferably maintained within the range of 10-300 mesh.

The trinitrophenolic salt component also functions as a plasticizer for the propellant compositions of the invention. I have found that the trinitrophenolic salt component plasticizes or softens the propellant composition sufficiently to allow as much as 87 parts of ammonium nitrate per parts of base propellant to be used. This is obviously advantageous because it permits manufacture of extrudable propellants of higher oxidizer content than has been possible heretofore.

Examples of salts of said trinitrophenolic compounds which can be used in my burning rate catalyst system include, among others, the following compounds: sodium styphnate (disodium salt of 2,4,6-trinitroresorcinol), potassium picrate, urea picrate, lead styphnate, calcium picrate, pyridinium styphnate, ammonium styphnate, lithium picrate, silver styphnate, chromium picrate, ammonium picrate, sodium picrate, copper picrate, zinc picrate, cadmium picrate, nickel picrate, aluminum pic- 3 rate, ferric picrate, tetraethyl ammonium picrate, N methyl pyridinium picrate, guanidinium styphnate, potassium styphnate, calcium stynhnate, guanylurea styphnate, isopropylamine, styphnate, n-heptylamine picrate, barium styphnate, strontium picrate, rubidium styphnate, magnesium styphnate, cesium picrate, and beryllium picrate.

When my burning rate catalyst system is employed in propellant compositions, it is customary to express the amount of catalyst present in the propellant in parts by weight per 100 parts by weight of base propellant. Thus, in propellant compositions when it is desired to express the amount of the components of my catalyst burning rate system based on the base propellant, the same ranges as given above can be employed. Herein base propellant is defined as binder plus oxidizer.

Oxidizers which are applicable in the solid propellant compositions of this invention are those oxygen-containing solids which readily give up oxygen and include, for example, ammonium, alkali metal, and alkaline earth metal salts of nitric, perchloric, and chloric acids, and mixtures thereof. Ammonium nitrate and ammonium perchlorate are the preferred oxidizers for use in the solid propellants of this invention. Other specific oxidizers include sodium nitrate, potassium perchlorate, lithium chlorate, calcium nitrate, barium perchlorate, and strontium chlorate. Mixtures of oxidizers are also applicable. In the preparation of the solid rocket propellant compositions, the oxidizers are ground to a particle size, preferably within the range between 20 and 200 microns average particle size. The most preferred particle size is from 40-60 microns. The amount of solid oxidizer used is usually a major amount of the total composition and is generally in the range between 50 and 85 percent by weight of the total propellant composition. If desired, however, the oxidizer can comprise less than 50 percent by weight of the propellant composition, in some instances. In the case of compression molded propellants, the propellant can contain 90 percent by weight and above of oxidizer based on total composition. Thus, the oxidizer content of the propellant composition usually ranges from 50 to 90 percent by weight.

A class of binder components widely used in solid propellant compositions and which form a presently preferred class of binders for use according to the invention comprises a rubbery copolymer of a conjugated diene and a heterocyclic nitrogen base. These copolymers are prepared by polymerizing a conjugated diene containing from 4 to 8 carbon atoms per molecule such as butadiene, isoprene, piperylene, methylpentadiene, chloroprene, and the like, with a monomer copolymerizable therewith. Preferred copolymerizable monomers are the polymerizable heterocyclic nitrogen compounds such as the vinyl pyridines, vinylquinolines, and the various alkyl-substituted derivatives of these compounds such as 2-methyl-S-vinylpyridine, 2-vinylpyridine, 2-vinyl-5- ethylpyridine, 2-vinylquinoline, and the like. These copolymers can be prepared by any suitable method, as for example, mass or emulsion polymerization. It is often desirable to incorporate carbon black in the copolymer during its preparation, this addition being accomplished by conventional methods, as for example, adding the carbon black to the latex prior to coagulation. The amount of carbon black can be from to 35 parts of black per 100 parts of copolymer. In the preparation of the copolymers, the amount of the conjugated diene will be at least 50 parts by weight per 100 parts of the monomer mixture, while the comonomer will be in the range of to 50 parts. Although, polymerizable heterocyclic nitrogen bases are the preferred comonomers, other comonomers such as styrene are applicable. Further details regarding the preparation of these copolymers can be found in the copending applications Serial No. 284,447, filed April 25, 1952 by W. B. Reynolds et 211.; Serial No. 475,000 filed December 13, 1954 by H. G. Cutforth et al.; and Serial No. 470,371, filed November 22, 1954 by R. S.

Hamner et al., wherein propellant compositions and methods of preparation of said propellant and binder com ponents are disclosed and claimed.

The finished binder usually contains various compounding ingredients. Thus, it will be understood that herein and in the claims, unless otherwise specified the term binder is employed generically and includes various conventional compounding ingredients. The binder content of the propellant composition will usually range from 10 to 50 percent by weight.

Any of the above described binders can be employed in the practice of my invention. In addition, many plastic, resinous, and other rubbery materials are suitable binder materials for the propellants of my invention. Thus, the invention is not to be limited to any particular binder. Examples of other suitable binders can be grouped as follows: asphalt and pitches including natural asphalts having a 170 F. softening point, air blown asphalts having a 270 F. softening point, mixtures of asphalt and synthetic or natural rubber, pitch having a 240 F. softening point, and mixtures of pitch and rubber; epoxy resins, such as Araldite 502 and Epon 834; liquid polymers such as polybutadiene, poly-butene, polyisobutylene, and Thiokol LP-3; polyethylenes; rubbers, both natural and synthetic, such as butyl rubber, ethyl acrylatemethylvinylpyridine copolymers, polybutadiene, and hydrogenated polybutadiene; waxes, both natural and synthetic having a melting point within the range of 150-300 F.; synthetic resins and plastics such as the various acrylic and polyvinyl resins; and nitro polymers such as polynitromethylmethylacrylate, nitropolybutadiene and polynitrovinyl alcohols.

The amount of the three-component burning rate catalyst which can be employed in the propellant compositions of this invention can vary widely. The amount of ammonium dichromate can vary in the range between 3 and 10 parts by weight per parts by weight of base propellant, while the copper or copper salt component can vary within the range of 0.5 to 7 on the same basis. The total parts by weight of the said two components per 100 parts by weight of propellant should not exceed 12. The amount of trinitrophenolic salt present should be at least 1.5 parts by weight per 100 parts by weight of base propellant and it is preferred to use not more than 20 parts on the same basis.

A preferred method of formulating the propellant compositions of this invention is to dry-blend the ammonium dichromate and the copper powder of selected copper compound with the oxidizer, incorporate this oxidizercopper or copper-compound ammonium dichromate mixture into the binder, and thereafter incorporate the trinitrophenolic salt into the resulting mixture. This method is preferred because it assures complete dispersion of the ammonium dichromate and copper or copper compound, and eliminates the possibility of comminuting the trinitrophenolic salt to too fine a particle size. However, if desired, the three components of the catalyst system can be pre-blended with each other and then blended with the oxidizer. Any desirable manner, or order, of incorporating the three components of the catalyst system into the propellant can be employed.

The propellant compositions can be formulated by milling the oxidant, burning rate catalyst, and other compounding ingredients into the binder on a roll mill or in some other suitable type of mixer, as for example, a blade-type mixer. It is sometimes advantageous to mill in the carbon black or other filler at this point rather than to add the carbon black to the latex prior to coagu" lation. Copolymers having a Mooney value (ML-4) in the range between 15 and 30 are preferred, as it is difiicult to incorporate the oxidant, etc., into higher Mooney polymers. Other compounding agents such as vulcanization agents, quaternization agents, vulcanization accelerators, softeners, stabilizers such as antioxidants, surface active agents, etc., can be advantageously added during the milling process.

5 f Afte'r' formulating the propellant composition; "the pre pellant can be extruded or compression molded into any desired geometric configuration. The three-component burning rate' catalyst of this invention is especially useful Two"aiid one-half parts by 'weight'pi '1 parts of rubberof additional low-abrasion furnace carbon black and 1.25 parts by weight on the same basis of a physical mixture containing 65% of a complex diarylamine ketonef in propellants which are to be extruded into propellant reaction product and 35% of N,N-diphenyl-p-phenylenef grains;- The extruded grains can then be cured by heat diamine were milled into the binder component prepared ing'to an elevated temperature for. an extended period of above. This increased the amount of carbon black time, as for example, 24 hours at 180 F. ent to 22 parts/100 parts of rubber and increased 4 A further advantage of the propellants of this invenamount of stabilizer presentto 3 parts/100 partsof tion is that these propellants can be cured without using rubber. the usual vulcanization agents, 'e.g. sulfur and a vulcaniza- The above described composition was then placed in tion accelerator, or quaternlzing agents in the case of a roll mill, and 20 parts/100 parts of rubber present of binders containing trivalent nitrogen atoms. di( 3,6-dioxadecyl)formal and 5'parts (on'the samebasis), A still further advantage of the three-component burnof magnesium oxide were milled into the binder. Com; ing'rate catalyst of this invention is that the effective exmercial grade ammonium nitrate, ground to 40 micron: haust velocity of rocket motors employing the propellants average particle size, was then dry-blended with all of oflhis'invention is not reduced as' would be expected the burning rate catalyst system components except "the' when the'percentage of oxidizer in the total propellant trinitrophenolic salt. This blend was then milled into mixture is decreased. 7 v p the binder until a propellant composition containing'83;5 The following examples will serve to further illustrate parts by weight ammonium nitrate was obtained. Said the invention. propellant composition contains 16.5 parts by weight of EXAMPLE I rubber binder, which'binder comprised rubbery copoly- Propellants containing various combinations of the substituted formal. (PlaStlciz-er)" F black three-component burning rate catalyst of the invention F EE f a and t id p f h It fi were prepared and compared with propellants containing e l P r 0 mm mp 8a s onvnfional Catalysts- I a m lled into the said' propellant composition. After the A 1,3 butadiene 2 methy1 5 vinypyridine rubbery tIlIlltlOpht3nO11C alt was intimately dispersed, the-propolymer was prepared by emulsion polymerization at 2212?; ffffifi'ggggg: fi zg gg 'i i i aigtg h f How 01 meri'zation reci e. 17 ace-0mm to ta 0 mg 9 y p at 180-F. for 24 hours. Said strands were then cut 7 POLYMERIZATION RECIPE into sections approximately 7" long, and all surfaces, Ingredient; [Parts b i h except one end, were restricted to prevent burning except 1,3-butadier1e 90 On S id end. The strands were then placed in a pressure 1 2- ethy1-5-vinylpyridine 10 bomb, and the bomb was pressured. to the desired pressure water 200 with nitrogen. The bomb was then placed in a temper- I P ta i fi-i synthetic bbe soap 6 ature bath maintainedat 70 F. The strands were then "po i l id 0,1 ignited, and the time required for the propellant to burn Sodium Salt of (Kmdensed alkylarylt between two fusible wires spaced 5" apart was recorded. lf i acid 03 The burning rate was then calculated in inches per second. Tetrasodium. salt of ethylenediaminetetra-,. '4 The results obtained with various burning rate catalysts acetie 0.005 are given below. in TableI.

Table 1 Burning Rate Catalyst Components (Parts/100 Parts of Base Propellant) Bu(r nir/1g R)ate in. see. a

9 Milori ammonium Copper Disodiurn. Copper Copper Urea Dipotasslum At 600 At 1,000 Blue 1 Diehromate Chromite Styphnate Oxide Powder Picrate Styphnate P.s.i. P.s.i. V

1 2. 0.144 0.210 '2 2 4 0.222 0.280 a 2 4 0.172 0.221 4 4 0.124 0.182 5 4 4 0.186 0.240 6 4 4 4 0. 291 0.371 7 6 4 4 0.277 0.322 s- 2 4 4 0. 204 0.250 9- 4 2 4 0.257 0. 33s 10 4 8 4 0.267 0.353 11 4 4 2 0.225 0.295 12 4 4 4 0. 236 0. 307; 1a 4 4 4 0.240 0.295 14 4 4 6 1 0.224 0.352 15 4 4 4 0.281 0.352

I Milorl Blue is :1 burning rate catalyst which is Widely used in propellants. Said Milori Blue is a pigmentsimilar lrussian Blue but having a red tint recipe. The latex was niasterbatclied with 19.5 parts of Phllblack A (a trademark ofPliillips Petroleum Company for a low abrasion furnace carbon black) per 100 parts of rubber. The black masterbatch was then acid congulated,

washed with water, and dried; The-average conversion for these 55 runs was-85%. in 17.0 hours. The amount of modifier used in-each run was in the range of 0.60 'to 0.80

part by weight.

Fifty-five runs were made using the above polymerization and is prepared by the oxidation of a paste of potassium ierrocyanide and ferrous sulfate.

The above Table I shows the increase in the burning rate which results when the three-component burningrate catalyst systems of this invention are'employed. lathe above table, Runs 1 through'S are control runs, while the remainder of the runs, with the exception of Run "8, represent the catalyst systems of the invention. Run 8 was a run in which the amount of ammonium dichromate wasbelow the operating range,.and itxis easily seen that this smaller amount of ammonium dicliromate 'afl' fected the burning rate adversely. 1

Runs 1 and 2 in the above Table I representcatal-ystsystems ofv the prior .art. For many usesthesecatalysts;

are regarded by those skilled in the art as superior catalysts. They give satisfactory or more than satisfactory results, particularly in those instances where moderate burning rates are desired. However, in some instances, such as in booster rockets, exceptionally high pellant of ammonium dichromate, 4 parts on the same basis of copper chromite, and 4 parts on the same basis oi disodium styphnate were then mixed into the p pellant. A ribbon of this propellant was then extrud cl burning rates are desired. A comparison of Runs 6, and and this ribbon was placed in an oven maintained at; Qthrough 15 (and the data given in Examples IV and 180? F. for 24 hours; The rlbbon was then evaluated hereinafter) with control Runs 1 to 5 shows the great for cure by standard tests. The results of, these tests are number of superior catalyst systems afforded by my in- S below In Table t vention for use when exceptionally high burning rates are It Was observed that the ribbon before oven treatment d i was soft and plastic, while after oven treatment, it was 4 it a firm and rigid, an evidence of cure. Properties of this EXAMPLE H V cured material -.are shown below in Table III. Several of the propellant compositions formulated in Example I were compression molded into propellant Table m grains. These grains werefired in a rocket motor, and P fi .3 the characteristic exhaust velocity was measured. These Tenslle Fuength -.-P- 2 tests were run to determine if the decrease of ammonium Elongatlon' ----P 7 f-. nitrate content in the propellants of this invention would Modulus (300%) "9- 5 3 decrease the characteristic exhaust velocity below the I a velocity normally developed by the conventional binder- EXAMPLE I oxidizer propellants; A control run (propellant from Another series of propellants containing various the-ee Run 2 in Table I) using the same binder, but with component burning rate catalyst systems of the inven- Mil o'ri Blue present as a catalyst was made. The contion containing various components were prepared as detfol run, since less catalyst/100 parts of base propellant scribed in Example I and the burning rates were d eused, contained more oxidizer per given amount of termined as described in Example I. The burning rates; finished propellant. The results of these tests are given of these additional propellants are given below in" below in Table II. Table IV.

Table IV Burning Rate Parts (inches/$00.) Run No. Ammonium Copper Binder Trinitrophonolsait Trinitro- Dichromate Chromate Used! phenol l r Salt at 600 at 1,000 l p.s.i. p.s.i.

4.0 4.0 A Urea sty'phnate 4.0 0.203 0.271 4.0 4.0 B Ure%picrate. 3.8 0.303 0.347

O A Potassium styphnat 4.0 0225 0'306 4.0 4.0 A Dircrylamine 6.0 0.225 0.205 4.0 4.0 A Sodium picrato.-- 10.0 0.362 0.400 4.0 4.0 0 do. 10.0 0.320 0.301

I The following binder formulations were used in the propellant compositions of Table IV:

Compositions (Bar ts by Weight) A B O 0000 Bd/MVP copolymer 100 100 100 PhilblackA". 22 22 22 Di(3,6-dioxadecyl)form l 00 20 MgO 5 5 None Antioxidant 3 3 3 Nitrocy n None 10 None lflfi parts oi phenyi-ii-naphthylamine were in at containing 65% of a complex-diarylamine-ketone reaction product and of diamine were milled in before the oxidant was milled in.

ts r h l i i iir iiigriiniiiii -pii iiii fie ."Tqb l. H

. Characteristics exhaust Ptop ellant from: velocity feed/second Run 2 ..L 4000 R1111 5 L' 3966* Additional run having identical composition to Run 6 4009 Estimated from other firing data.

EXAMPLE m A propellant containing 16.5 weight percent of-the compounded binder of Example I and 83.5 weight percent of commercial ammonium nitrate which had been ground to 40.micron average particle size was placed in a liakerderkins, mixer. Four parts/100 parts of pro.-

the time the rubber wagmaat, and 1.25 additional In the runs listed in Table 1Y the same Bd/MVP copolymer described in Example I was used. In Runs 16-20, the ratio of binder component to oxidizer component in parts by weight was 16.510835. In Run 21, said ratio was 15 to 85. The increased amount of oxidizer component used in Run 21 illustrated the previously described plasticization advantage realized when the trinitrophenolic salt of the burning rate catalyst system is used. p

' EXAMPLE V An amount of the butadiene-Z-methyl-S-vinylpyridine copolymer of Example I, containing 22 parts of lowabrasion furnace carbon black per parts rubber and 3 parts per 100 parts of rubber of a physical mixture containing 65% by weight of a complex diarylamineketone reaction product and 35% by weight of N,N' diphenyl-p-phenylenediamine, was placed in, a rollmill, and 20 parts per 100 parts of; rubber of di-(3,6-dioxadecyl)formal and 5 parts per 100 parts of rubberof mag e m x de w re mi ed W9 th rub e aoeogess .Five propellants were made in which the binder, pre-' pared as described above was used. These propellants were made up according to the following recipes.

RECIPES Composition in Parts by WeightPropellant Number In propellant #1, the proper amount of oxidant was milled into the binder by adding the oxidant in portions to the binder while the mill was running. The total milling time was 3.5 minutes. Propellants 2 and 3 were made by dry blending the proper amount of ammonium dichromate (#2) or copper chromite (#3) with the oxidant and then adding the blend portionwise to the binder on the mill. Total milling time was the same as for propellant #1. Propellant #4 was prepared by milling oxidant into the binder as in #1 (3.5 minutes mill time) and thereafter milling in the sodium picrate with the minimum amount of milling to insure intimate dispersion. Propellant #5 was made by dry blending the ammonium dichromate and copper chromite with ammonium nitrate and thereafter milling this blend into the binder (mill time 3.5 minutes). The sodium picrate was then milled into the resulting material as in propellant #4.

The propellants, prepared as described, were then extruded into strands approximately 3%" in diameter. The strands were then cured at 200 F. for 24 hours. The cured strands were then cut into sections approximately 7" long, and all surfaces, except one end, were restricted to prevent burning except on said end. The strands were then burned in a bomb as described in Example I to determine their burning rate.

The results of these burning rate tests are given below in Table V.

It can be seen by examining the above burning rate data that the three-component catalyst system of the present invention produces an unexpectedly high burning rate. This can be seen if the rate increases (AR) for propellants 2, 3, and 4 are summed up and compared to AR for propellant 5. At 600 p.s.i., the sum of the AR's for 2, 3, and 4 is 0.234, while the AR for #5 is 0.281. This represents an unexpected increase of 20.1%. Similarly, at 1000 p.s.i., an unexpected increase of 18.8% is obtained.

EXAMPLE v1 An amount of the binder of Example I, containing 100 parts by weight of the butadiene-vinylpyridine rubber of Example I, 22-parts by weight per 100 parts of rubber of low abrasion furnace carbon black, 3 parts by weight per 100 parts of rubber of a physical mixture containing 65% by weight of a complex diarylamine-ketone reaction product and 35% by weight of N,N'-diphenyip-phenylenediamine, 20 parts by weight per parts of rubber of di-(3,6-dioxadecyl)formal and 5 parts by weight per 100 parts of rubber of magnesium oxide was placed in a 0.7 gallon Baker-Perkins mixer. An amount of ammonium nitrate, having an average particle size of 40 microns, was then milled into the binder (nitrate added in increments) until a composition containing 16.5 weight percent binder and 83.5 weight percent ammonium nitrate was reached. This material, labeled base propellant, was then removed from the mixer and split into five portions. The first portion was placed in a roll mill and milled for 3 minutes without adding any other components. This portion, base propellant, was labeled Run 1. The second portion, labeled Run 2, was placed in a roll mill and the desired amount of ammonium dichromate was milled in, using a milling time of 3 minutes. Run 3 was carried out in the same manner as Run 2, copper chromite being the added component instead of ammonium dichromate. The fourth portion, labeled Run 4, was placed in a roll mill and milled for 3 minutes, after which the desired amount of sodium picrate was milled in, using a milling time of the shortest possible duration to insure intimate dispersion (approximately 20 seconds). The fifth portion (Run 5) was placed in a roll mill and the proper amounts of copper chromite and ammonium dichromate were milled into the base propellant using a total milling time of 3 minutes. The proper amount of sodium picrate was then milled into the mixture, using the very short mill time (20 seconds) as was used in Run 4.

The above-described propellants were then extruded into strands, cured, restricted, and burned in a bomb as described in Example V. The compositions and results of the burning rate tests are given below in Table Table VI Composition in Parts by Component 1 Binder 16. 5 16. 5 l6. 5 16. 5 16.-5 Oxi'iant (NH NO 83 5 83.5 83-5 83.5 83.5 Ammonium Dic-l1romate 0 4 O 0 4 Copper Chromite 0 0 4 0 4' Sodium Picrato 0 0 0 10 10 NT N0;particle size approx. 40 microns. Ammonium dichromate-particle size approx. 15 microns. Copper chromite-particle sizeapprox. 3-4 microns. Sodium picrate-particle size approx. 65-100 mes Burning Rate Data (inches/sec.)

Propellant No.

Increase over Bas Proat 600 p.s.i.

pellant (AR) (control 0. 074 0. 179 0. 132 0 133 0. 321 O. 247

It can be seen from the above data that ponent burning rate catalyst system of the present invention produces an unexpectedly fast burning rate. Summing the ARs (as in Example V) for propellants 2, 3, and 4, the additive increase at 600 p.s.i. over the control propellant is 0.220. The AR for propellant 5 over the control propellant is 0.247, an unexpected increase of 12.3 percent.

The two examples, Examples V and VI, clearly demonstrate the synergism of the catalyst system of the present invention. Example V represents a preferred method of incorporating the catalyst system of the present in- Weight-Propellant Number the 3-comvention into a propellant material. Example VI, which illustrates a less preferred method of incorporating the catalyst system into a propellant, likewise illustrates the synergistic properties of the catalyst system of this invention.

As will be evident to those skilled in the art various modifications of the invention can be made, or followed,

in the light of the above disclosure withoutdeparting from the spirit or scope of said invention.

I claim:

l. A propellant burning rate catalyst system consisting essentially of, in parts by weight based on said system: from 3 to 10 parts of ammonium dichromate; from 0.5 to 7 parts of a copper component selected from the group consisting of finely divided copper metal, copper chromite, and copper oxides; and from 2 to 20 parts of a saltof the trinitrophenolic compounds selected from the group consisting of 2,4,6-trinitro'phenol and 2,4,6-trinitroresorcinol.

. 2. A propellant burning rate catalyst system according to claim 1 wherein said salt is' sodium picrate.

3. A propellant burning rate catalyst system according to claim 1 wherein said salt is sodium styphnate.

4. A propellant burning rate catalyst system according to claim 1 wherein said salt is urea picrate.

5. A propellant burning rate catalyst system according to claim 1 wherein said salt is urea styphnate.

6. A propellant burning rate catalyst system according to claim 1 wherein said salt is potassium styphnate.

7. A propellant burning rate catalyst system according to claim 2 wherein said copper component is copper chromite.

8. A propellant burning rate catalyst system according to claim 3 wherein said copper component is copper chromite.

9. A propellant burning rate catalyst system according to claim 4 wherein said copper component is copper chromite.

10. A propellant burning rate catalyst system according to claim 5 wherein said copper component is copper chromite.

11. A propellant burning rate catalyst system according to claim 6 wherein said copper component is copper chromite.

12. A propellant burning rate catalyst system consisting essentially of in parts by weight, equal parts of: ammonium dichromate; copper chromite; and sodium styphnate.

13. An improved solid composite type propellant composition comprising: as a base propellant, a solid inor ganic oxidizing salt as an oxidizer component and a suitable binder component; and a burning rate catalyst system consisting essentially of from 3 to 10 parts by weight per 100 parts by weight of said base propellant of ammonium dichromate, from 0.5 to 7 parts by weight per 100 parts by weight of said base propellant of a copper component selected from the group consisting of finely divided copper metal, copper chromite, and copper oxides, and from 2 to parts by weight per 100 parts by weight of said base propellant of a salt of a trinitroplifioliti com;

pound selected from the group consisting of 2,4,6-trinitrophenol and 2,4,6-trinitroresorcinol. l 14. An improved solid propellant composition according to claim 13 wherein: said ammonium dichromate is present in an amount of 4 parts by weight per parts by weight of said base propellant; said copper componentv is copper chromite and is present in an amount of 4 parts by weight per 100 parts by weight of said base propellant; and said salt of a trinitrophenolic compound is sodium styphnate and is present in an amount of 4 parts by weight per 100 parts by weight of said base propellant.

15. An improved solid propellant according to claim 13 wherein said salt is sodium picrate.

16. An improved solid propellant according to claim 13 wherein said salt is sodium styphnate.

17. An improved solid propellant according to claim 13 wherein said salt is urea picrate.

18. An improved solid propellant according to claim 13 wherein said salt is urea styphnate.

19. An improved solid propellant according to claim 13, wherein said salt is potassium styphnate.

20. An improved solid propellant according to claim 15 wherein said copper component is copper chromite.

21. An improved solid propellant according to claim 16 wherein said copper component is copper chromite;

22. An improved solid propellant according to claim 17 wherein said copper component is copper chromite.

23. An improved solid propellant according to claim 18 wherein said copper component is copper chromite.

24. An improved solid propellant according to claim 19 wherein said copper component is copper chromite.

25. In the method of developing thrust wherein a solid propellant charge contained in a combustion chamber of a rocket motor is ignited and then burned with the evolution of combustion gases which are exhausted from said combustion chamber, the step which comprises burning in said combustion chamber a propellant chargev comprising: as a base propellant, a solid inorganic oxidizing salt as an oxidizer component and a suitable binder component; and a burning rate catalyst system consisting essentially of from 3 to 10 parts by weight per 100 parts by weight of said base propellant of ammonium dichromate, from 0.5 to 7 parts by weight per 100 parts. by weight of said base propellant of a copper component selected from the group consisting of finely divided cop-. per metal, copper chromite, and copper oxides, and. from 2 to 20 parts by weight per 100 parts by weight of said. base propellant of a salt of a trinitrophenolic compound selected from the group consisting of 2,4,6-trinitrophenol and 2,4,6-trinitroresorcinol.

26. A propellant burning rate catalyst system consisting essentially of equal parts by weight of: ammonium dichromate; a copper component selected from the group consisting of finely divided copper metal, copper chromite, and copper oxides; and a salt of a trinitrophenolic compound selected from the group consisting of 2,4,6-trinitrophenol and 2,4,6-trinitroresorcinol.

References Cited in the file of this patent UNITED STATES PATENTS 2,637,274v Taylor et al. t May 5, 1953 OTHER REFERENCES Bebie: Manual of Military Pyrotechnics and Chemical Warfare Agents, MacMillan C0,, N.Y. (1943), ppQ27-28. (Copy in Scientific Library.)

Hutchison May 8, 6 

25. IN THE METHOD OF DEVELOPING THRUST WHEREIN A SOLID PROPELLANT CHARGE CONTAINED IN A COMBUSTION CHAMBER OF A ROCKET MOTOR IS IGNITED ND THEN BURNED WITH THE EVOLUTION OF COMBUSTION GASES WHICH ARE EXHAUSTED FROM SAID COMBUSTION CHAMBER, THE STEP WHICH COMPRISES BURNING IN SAID COMBUSTION CHAMBER A PROPELLANT CHARGE COMPRISING: AS A BASE PROPELLANT, A SOLID INORGANIC OXIDIZING SALT AS AN OXIDIZER COMPONENT AND A SUITABLE BINDER COMPONENT; AND A BURNING RATE CATALYST SYSTEM CONSISTING ESSENTIALLY OF FROM 3 TO 10 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF SAID BASE PROPELLANT OF AMMONIUM DICHROMATE, FROM 0.5 TO 7 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF SAID BASE PROPELLANT OF A COPPER COMPONENT SELECTED FROM THE GROUP CONSISTING OF FINELY DIVIDED COPPER METAL, COPPER CHROMITE, AND COPPER OXIDES, AND FROM 2 TO 20 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF SAID BASE PROPELLANT OF A SALT OF A TRINITROPHENOLIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF 2,4,6-TRINITROPHENOL AND 2,4,6-TRINITRORESORCINOL. 